The invention relates in general to wireless networks, and in particular to a method and system for handling different call scenarios in packet/voice networks.
Wireless communication networks provide the ability for one or more wireless or mobile nodes (generically “mobile units”) to communicate with other mobile units or other nodes connected to wireless and/or wired networks. There are generally two types of wireless communication networks: circuit-switched and packet-switched.
Circuit-switched wireless communication networks typically include one or more Mobile Switching Centers (MSCs) for connecting to other switching centers and other networks, including the landline Public Switched Telephone Network (PSTN). Typical call control protocols in a circuit-switched network include ISUP (ISDN User Part) and Feature Group D.
Packet-switched wireless communication networks typically include a plurality of call servers and Media Gateways (MGs). SIP (Session Initiation Protocol) and BICC (Bearer Independent Call Control) are examples of call control protocols used in a packet-switched network.
The current approach to introducing packet based (e.g. Internet Protocol) multimedia services for wireless communication networks such as Universal Mobile Telecommunications Service (UMTS), Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA) is to define an IP Multimedia Subsystem (IMS). IMS includes a plurality of IP-connected network entities using packet-switched services. These network entities provide IP Multimedia features and services using such vehicles as Session Initiation Protocol (SIP) for call control.
The IMS shares little in common with the traditional MSC supporting circuit-switched services. Also, the IMS introduces design difficulties that are new and or different from those in circuit-switched services. For example, when a mobile unit goes through handoff in a packet based network, a dynamic packet trunk (DPT) serving the call may not be able to be re-routed during the call. It is desired to reduce associated difficulties and support various call-handling scenarios in the packet network and other networks similarly configured.